So, I think all good tornado talks need to start
with an awesome tornado shot.
And this is not that awesome tornado shot.
That was the first tornado I ever saw, it was really cool, really scary,
and I'm showing it to you guys
because that's why I got into the field in the first place.
So even though it's a bad photograph,
it was really cool to be out there the first time.
But now I'm taking real tornado footage.
Fast forward a few years.
This is a few years ago, during a field project called VORTEX2,
where myself and a bunch of other scientists were out there,
surrounding tornadoes with different types of instrumentation
and trying to figure out how tornadoes form.
It's a big question we're trying to answer.
It sounds like a very basic one,
but it's something we're still trying to figure out.
We're also still trying to figure out what the winds are like near the surface.
We know what the winds are like above building level,
but we really don't know what they're like at the surface
and how that relates to what we're seeing above building level.
Most tornadoes form from what we call supercell thunderstorms.
Supercell thunderstorms are what you commonly think of
as tornado-raising storms.
They're big, rotating thunderstorms
that happen a lot of times in the midsection of the United States.
But the problem is that even though they're rotating up above,
it doesn't mean they're rotating at the surface.
And when we look at these storms
and at these pictures and at the data we have,
they all kind of look the same.
And it's really problematic
if we're trying to make tornado forecasts or warnings,
because we only want to warn or forecast about the storms
that are going to actually make a tornado.
One of the big, critical distinguishing features, we think, between these storms,
is something about the rear-flank downdraft.
So these big rotating thunderstorms have this downdraft
that wraps around the rear edge of it,
hence the "rear-flank" downdraft.
But we think how warm that is, how buoyant that air is,
and then also how strong the updraft it's wrapping into,
makes a big difference on whether or not it's going to make a tornado.
There's a lot more that goes into it --
I'll tell you about that in a second.
Once you actually get a tornado, again, the problem that we have
is getting measurements near the surface.
It's really hard to get measurements near the surface --
most people don't want to drive into tornadoes.
There are a few exceptions; you might have seen them on TV shows.
But most people don't want to do that.
Even getting instrumentation in the path of the tornado is pretty tricky, too.
Because, again, you don't want to be that close to a tornado
because sometimes the winds around the tornado are strong as well.
So getting information, that critical location,
is key for us because, again, we don't know
if the winds that we're seeing above ground level,
way above building level,
actually map to the surface,
if they're stronger, weaker, or about the same
as what we're seeing above buildings.
The way we get at answering a lot of these questions --
and I'm an observationalist; I love to get out in the field,
and collect data on tornadoes --
we compile a lot of observations.
I work with this group who operates mobile radars,
and they're exactly what they say -- basically, a radar
on the back of a big blue truck,
and we drive up really close to tornadoes to map out the winds.
We map out the precipitation.
We map out all these different things that are going on
in order to better understand the processes in these storms.
And that bottom there, that's what a tornado looks like
when you're looking at it with a mobile radar, and really close.
Also, what we do is a lot of modeling,
so we do a lot of computer models and simulations,
because the atmosphere is governed by the laws of physics.
So we can model the laws of physics
and see where the tornado might go,
where the storm might go,
how strong the winds are near the surface
and not actually have to go out in the field.
But of course, we want to have both observations and modeling
to move forward with the science.
So, I showed you that video earlier that went real quick, too.
This is what it looks like, looking at it with a radar.
So you saw it visually,
but this is what I get really excited about when I see now in the field,
stuff that looks like this.
The really exciting thing about looking at stuff like this
is that we caught this storm from when it didn't make a tornado
to when it made a tornado and intensified
and when it dissipated.
This is the one of the rare data sets that we have out there
that were able to study the entire life cycle of a tornado.
I talked about how we think that rear-flank downdraft is important
because it tilts, there's a lot of spin in the atmosphere,
but the problem with all this spin in the atmosphere
is it needs to be oriented vertically,
because that's what tornadoes are doing,
and it needs to orientated vertically near the ground.
So we think this rear-flank downdraft just pulses.
And these pulses in this rear-flank downdraft, we think,
are very important for converging that rotation,
but also getting that rotation into the right place.
Other things we've learned
is that we have gotten a bunch of fortuitous measurements
in the path of the tornadoes and very near the surface.
And we found out
that the winds near the surface are actually pretty comparable
to what we're seeing 30, 40 meters above ground level.
So there's not a big reduction in what we're seeing above the surface
to what we're seeing at house level.
And that was a pretty surprising finding for us,
because we kind of assumed that the winds decrease
pretty substantially near the surface.
I'm going to end with this real quick.
And this is not my last tornado I ever saw,
but I really like this image,
because this was taken with one of those mobile radars I was talking about.
This is a tornado, not a hurricane,
and this is what it looks like when you're really close to it.
And I find this amazing,
that we can actually take technology this close to these types of storms
and see these inner workings.
And for those of you who look at tornado images often,
you can see there's a lot going on -- there's rain spiraling,
and you can actually see the debris cloud associated with this tornado.
I look forward to the future and future technologies
and being able to learn a lot more about these storms,
as the world advances,
as you guys contribute to the science
and we're able to really learn more about how tornadoes form.
Thank you.
(Applause)